The present invention relates generally to apparatus for handling and transporting folded sheet material, and in particular to method and apparatus for merging two shingled signature streams into a single running output stream for transport to an inline processing station.
In the operation of a web-fed offset or rotogravure printing press of the type used for printing newspaper inserts, magazines, booklets and the like, a printed web is fed into a folder at the delivery end of the press where it is folded, cut, slit and output in an overlapping assembly of identical folded items, thereby forming a running shingle. Each folded item is referred to as a "signature" and the overlapping signatures are said to be "shingled". In a running shingle, the signatures partially overlap, with the folded edge of trailing signatures being set back with respect to the folded edge of the leading signatures.
As the running shingle exits from the folder, the shingled signatures are transported by a conveyor belt to an inline processing station where various finishing operations are performed. Examples of such finishing operations include trimming at a rotary trimmer; attaching address labels at a labeling machine; and, stacking signatures in bundles for delivery to a bulk mailing station, or for delivery to a newspaper or magazine vendor, or for temporary storage awaiting further assembly with freshly printed signatures in a saddle stitching and perfect binding machine.
The folders of most modern web presses incorporate a slitting wheel which slits the printed web, forming two or more ribbons that are fed into the folder, where they are folded and a rotary knife cuts the folded ribbons. The ribbons may be folded in various forms, i.e. half-folded and quarter-folded signatures. The folder delivers the folded signatures to a folder delivery where they are output in two or more shingled signature streams. Each shingled stream is then separately conveyed, either one elevated above the other or one laterally offset from the other, to separate in-line finishing stations.
Moreover, in some installations, two web presses are operated side-by-side, each producing a shingled stream of signatures, with the singles being transported along parallel conveyors to separate in-line finishing stations. Consequently, press operators have found it necessary to provide duplicate finishing units requiring a large expenditure for capital equipment, with the duplicate finishing units occupying duplicate floor space areas and requiring duplicate crews to perform finishing operations at the separate finishing stations.
It will be appreciated that production costs could be reduced substantially by merging the separate product streams into a single output stream for subsequent processing by one crew at a single in-line processing station. Various proposals have been made for handling multiple streams of signatures so that a single running stream of signatures is presented for subsequent processing.
For example, Gammerler U.S. Pat. No. 4,696,464 discloses a method of merging two shingled product streams and delivering them as a single stream of shingled product. Gammerler's method requires that the movement of shingles in an upper product stream be synchronized with the movement of shingles in a lower product stream, whereby shingles from the upper product stream can be ejected onto signatures in the lower product stream.
Hansch U.S. Pat. No. 4,684,116 discloses method and apparatus for collating signatures having three conveyors of signatures that are input to a rotating, collating drum which feeds the signatures to a single conveyor. The signatures are re-shingled by a withdrawal conveyor into a single output stream.
Honegger U.S. Pat. No. 5,292,110 discloses method and apparatus for handling multiple streams of signatures in series or in parallel. A revolving endless conveyor combines two or more streams of printed items into a single running shingle for subsequent processing.
Lindblom U.S. Pat. No. 5,098,075 discloses a stream of signatures that are spaced and diverted to one of two impeller wheels that deliver signatures to a single stack. The signatures are combined as desired including two different partial inner books made up from assembled signatures.
One limitation on the use of conventional merging units is the requirement for synchronization or isochronous coordination of shingles in two or more product streams. This generally requires considerable additional construction and equipment costs, as well as being difficult to achieve in actual practice, particularly in view of the difficulty of synchronizing equipment operation and shingle movement at high operating speeds. Further difficulties arise where the shingled signature streams are being output at different feed rates from separate sources. Consequently, there is a continuing interest in providing method and apparatus for merging two independent signature streams into one shingled output stream for further processing in a single finishing unit.